Mixed metal oxide catalysts

ABSTRACT

Catalytic compositions are provided that are effective for providing increased acrylonitrile product without a significant decrease in hydrogen cyanide and/or acetonitrile production and provide an overall increase in production of acrylonitrile, hydrogen cyanide and acetonitrile. The catalytic compositions include a complex of metal oxides and include at least about 15% m-phase plus t-phase by weight and have a weight ratio of m-phase to m-phase plus t-phase of 0.45 or greater.

Catalytic compositions for ammoxidation of an unsaturated hydrocarbon toa corresponding unsaturated nitrile are provided. More specifically,catalytic compositions are provided that include a complex of metaloxides effective for conversion of propylene to acrylonitrile, hydrogencyanide and acetonitrile.

BACKGROUND

Catalysts containing oxides of iron, bismuth and molybdenum, promotedwith suitable elements, have long been used for conversion of propyleneand/or isobutylene at elevated temperatures in the presence of ammoniaand oxygen to manufacture acrylonitrile and/or methacrylonitrile. Inparticular, Great Britain patent 1436475; U.S. Pat. Nos. 4,766,232;4,377,534; 4,040,978; 4,168,246; 5,223,469 and 4,863,891 are eachdirected to bismuth-molybdenum-iron catalysts which may be promoted withGroup II elements to product acrylonitrile. In addition, U.S. Pat. Nos.5,093,299, 5,212,137, 5,658,842 and 5,834,394 are directed tobismuth-molybdenum promoted catalysts exhibiting high yields toacrylonitrile. These catalysts may provide increased acrylonitrileproduction but with a corresponding decrease in yield of hydrogencyanide and/or acetonitrile coproducts.

SUMMARY

Catalytic compositions are provided that are effective for providingincreased acrylonitrile product without a significant decrease inhydrogen cyanide and/or acetonitrile production and provide an overallincrease in production of acrylonitrile, hydrogen cyanide andacetonitrile.

A catalytic composition is provided that includes a complex of metaloxides having a formula:Mo_(m)Bi_(a)Fe_(b)A_(c)D_(d)E_(e)F_(f)G_(g)Ce_(h)O_(x)

wherein A is at least one element selected from the group consisting ofsodium, potassium, rubidium and cesium;

D is at least one element selected from the group consisting of nickel,cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium andbarium;

E is at least one element selected from the group consisting ofchromium, tungsten, boron, aluminum, gallium, indium, phosphorus,arsenic, antimony, vanadium and tellurium;

F is at least one element selected from the group consisting of a rareearth element, titanium, zirconium, hafnium, niobium, tantalum,aluminum, gallium, indium, thallium, silicon, germanium, and lead;

G is at least one element selected from the group consisting of silver,gold, ruthenium, rhodium, palladium, osmium, iridium, platinum andmercury;

a is from 0 to 7;

b is from 0.1 to 7;

c is from 0.01 to 5;

d is from 0.1 to 12;

e is from 0 to 5;

f is from 0 to 5;

g is from 0 to 0.2;

h is from 0.01 to 5;

m is from 12 to 13; and

x is a number of oxygen atoms required to satisfy valence requirementsof other component elements. The catalytic composition includes at leastabout 15% m-phase plus t-phase by weight and has a weight ratio ofm-phase to m-phase plus t-phase of 0.45 or greater. Amounts of m-phaseand t-phase are determined using x-ray diffraction and a modifiedRietveld analysis model. The catalytic composition is effective forproviding an acrylonitrile yield (% AN) of 81 or greater and anacrylonitrile yield (% AN) plus acetonitrile yield (% ACN) plus hydrogencyanide yield (% HCN) of 88 or more.

In another aspect, a process is provided for production of acrylonitrileusing the catalyst compositions described herein. The process includescontacting propylene, ammonia and oxygen in a vapor phase in thepresence of the metal oxide catalyst.

In another aspect, a process is provided for analyzing a metal oxidecatalyst. The process includes generating x-ray diffraction data andanalyzing the x-ray diffraction data using a modified Rietveld analysis.The modified Rietveld analysis model includes a β-MMoO₄ phase, aFe₂(MoO₄)₃ phase, an m-phase and a t-phase.

BRIEF DESCRIPTION OF FIGURES

The above and other aspects, features and advantages of several aspectsof the process will be more apparent from the following drawing.

FIG. 1 demonstrates a trend of increased acrylonitrile yield withincreasing concentrations of m-phase with an associated fitted trendline.

Corresponding reference characters indicate corresponding componentsthroughout the several views of the drawings. Skilled artisans willappreciate that elements in the figures are illustrated for simplicityand clarity and have not necessarily been drawn to scale. For example,the dimensions of some of the elements in the figures may be exaggeratedrelative to other elements to help to improve understanding of variousaspects of the present process and apparatus. Also, common butwell-understood elements that are useful or necessary in commerciallyfeasible aspects are often not depicted in order to facilitate a lessobstructed view of these various aspects.

DETAILED DESCRIPTION

Metal oxide catalysts are provided for the production of acrylonitrile.The catalysts have a general formula and are further characterized ashaving at least about 15% m-phase plus t-phase by weight and a weightratio of m-phase to m-phase plus t-phase of 0.45 or greater. Inaccordance with this aspect, the oxide catalyst is analyzed using X-raydiffraction (XRD). Results of the XRD analysis are then interpretedusing a modified Rietveld analysis to determine amounts of m-phase andt-phase. The metal oxide catalysts provide an acrylonitrile yield (% AN)of 81 or greater and an acrylonitrile yield (% AN) plus acetonitrileyield (% ACN) plus hydrogen cyanide yield (% HCN) of 88 or more.

DEFINITIONS

Unless otherwise defined, the following terms as used throughout thisspecification for the present disclosure are defined as follows and caninclude either the singular or plural forms of definitions belowdefined:

As used herein “m-phase” refers to a component that is monoclinicscheelite like as determined by a modified Rietveld analysis describedherein.

As used herein “t-phase” refers to a component that is tetragonalscheelite like as determined by a modified Rietveld analysis describedherein.

As used herein, “acrylonitrile yield” means the percent molar yield ofacrylonitrile (expressed as number without any percent sign) calculatedas follows: (moles of acrylonitrile produced/moles of propylene fed tothe reactor)×100.

As used herein, “acetonitrile yield” means the percent molar yield ofacetonitrile (expressed as number without any percent sign) calculatedas follows: (moles of acetonitrile produced/moles of propylene fed tothe reactor)×100.

As used herein, “hydrogen cyanide yield” means the percent molar yieldof hydrogen cyanide (expressed as number without any percent sign)calculated as follows: (moles of hydrogen cyanide produced/moles ofpropylene fed to the reactor)×100.

As used herein, “catalytic composition” and “catalyst” are synonymousand used interchangeably. As used herein, a “rare earth element” meansat least one of lanthanum, cerium, praseodymium, neodymium, promethium,samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium,thulium, ytterbium, scandium and yttrium.

Catalytic Compositions

The multi-component mixed metal oxide ammoxidation catalyticcompositions include a complex of catalytic oxides represented by thefollowing formula:Mo_(m)Bi_(a)Fe_(b)A_(c)D_(d)E_(e)F_(f)G_(g)Ce_(h)O_(x)

wherein A is at least one element selected from the group consisting ofsodium, potassium, rubidium and cesium;

D is at least one element selected from the group consisting of nickel,cobalt, manganese, zinc, magnesium, calcium, strontium, cadmium andbarium;

E is at least one element selected from the group consisting ofchromium, tungsten, boron, aluminum, gallium, indium, phosphorus,arsenic, antimony, vanadium and tellurium;

F is at least one element selected from the group consisting of a rareearth element, titanium, zirconium, hafnium, niobium, tantalum,aluminum, gallium, indium, thallium, silicon, germanium, and lead;

G is at least one element selected from the group consisting of silver,gold, ruthenium, rhodium, palladium, osmium, iridium, platinum andmercury;

a, b, c, d, e, f, g, h and n are, respectively, the atomic ratios ofbismuth (Bi), iron (Fe), A, D, E, F, cerium (Ce) and oxygen (O),relative to 12 atoms of molybdenum (Mo), wherein

a is from 0 to 7, in another aspect, 0.05 to 7;

b is from 0.1 to 7, in another aspect, 0.5 to 1.5;

c is from 0.01 to 5, in another aspect, 0.1 to 0.5;

d is from 0.1 to 12, in another aspect, 3 to 8;

e is from 0 to 5, in another aspect, 0.01 to 0.1;

f is from 0 to 5, in another aspect, 1 to 4;

g is from 0 to 0.2, in another aspect, 0.05 to 0.15;

h is from 0.01 to 5, in another aspect, 1 to 2;

m is from 12 to 13; and

x is a number of oxygen atoms required to satisfy valence requirementsof other component elements.

The catalytic composition includes at least about 15% m-phase plust-phase by weight, in another aspect, at least about 18% m-phase plust-phase by weight, in another aspect, at least about 20% m-phase plust-phase by weight, and in another aspect, at least about 22% m-phaseplus t-phase by weight. The composition has a weight ratio of m-phase tom-phase plus t-phase of 0.45 or greater, where amounts of m-phase andt-phase are determined using x-ray diffraction and a modified Rietveldanalysis model. The catalytic composition is effective for providing anacrylonitrile yield (% AN) of at least 81% or greater, in anotheraspect, at least about 82% or greater, in another aspect, at least about83% or greater, in another aspect, about 88% to about 95%, and inanother aspect, about 88% to about 90%. The catalytic composition isfurther effective for providing an acrylonitrile yield (% AN) plusacetonitrile yield (% ACN) plus hydrogen cyanide yield (% HCN) of 88 ormore, in another aspect, about 88 to about 95, and in another aspect,about 88 to about 90.

In another aspect, amounts of m-phase plus t-phase and amounts ofm-phase/(m-phase+t-phase) may be as follows:

m-phase + t-phase m-phase/(m-phase + t-phase) about 15 to about 35 about45 to about 70 about 15 to about 25 about 45 to about 60 about 15 toabout 20 about 45 to about 55 about 20 to about 35 about 45 to about 50about 20 to about 30 about 50 to about 55 about 20 to about 25 about 55to about 60 about 60 to about 65 about 65 to about 70

In various aspects, the catalytic composition may include the following:0.15≦(a+b)/d≦1;0.8≦h/b≦5;0.2≦(a+h)/d≦0.6;0.3≦(a+h)/d≦0.5;1≦h/b≦3; and1.5≦h/b≦2.

In the aspect where 0.8≦h/b≦5, “h/b” represents a ratio of cerium toiron in the catalytic composition which is moles of cerium (asrepresented by the subscript for cerium in the formula) divided by molesof iron (as represented by the subscript for cerium in the formula).

The catalyst may be supported or unsupported. Suitable supports aresilica, alumina, zirconia, titania, and mixtures thereof. A supporttypically serves as a binder for the catalyst and results in a stronger(i.e. more attrition resistant) catalyst. However, for commercialapplications, an appropriate blend of both the active phase (i.e. thecomplex of catalytic oxides described herein) and the support isimportant for obtaining an acceptable activity and hardness (attritionresistance) for the catalyst. In this aspect, the supported catalystincludes between about 30 and about 70 weight percent of the support,and in another aspect between about 40 and about 60 weight percent ofthe support.

In one aspect, the catalyst is supported using a silica sol. Silica solsused include less than about 600 ppm sodium, and in another aspect, lessthan about 200 ppm sodium. The silica sols will have an average particlediameter between about 4 nm and about 100 nm, and in another aspect,between about 15 nm and about 50 nm.

Catalyst Preparation

Catalyst compositions may be prepared using any process of catalystpreparation known in the art. Examples of catalyst preparation aredescribed in U.S. Ser. No. 13/065,134, filed Mar. 15, 2011 and U.S. Ser.Nos. 12/661,705, 12/661,720 and 12/661,716, all filed Mar. 23, 2010, andall of which are incorporated herein by reference and summarized herein.

Elements in the catalyst composition are combined together in an aqueouscatalyst precursor slurry. The aqueous catalyst precursor slurry isdried to form a catalyst precursor and the catalyst precursor iscalcined to form the catalyst. In this aspect, source compounds of Biand Ce, and optionally one or more of Na, K, Rb, Cs, Ca, a rare earthelement, Pb, W, and Y are combined in an aqueous solution to form afirst mixture. A source compound of molybdenum is added to the firstmixture to form a precipitate slurry. The precipitate slurry is combinedwith source compounds of the remaining elements and of the remainingmolybdenum in the catalyst to form an aqueous catalyst precursor slurry.

Modified Rietveld Analysis

Catalytic compositions may be analyzed using X-ray diffraction (XRD) anda modified Rietveld analysis. In this aspect, crystallographic phases ofa catalytic composition are analyzed using XRD analysis as known in theart. A diffraction pattern of the catalytic composition is then analyzedwith the modified Rietveld analysis described herein.

In accordance with the modified Rietveld analysis, a completediffraction pattern is simulated through an ab initio calculation on thebasis of the atomic structures of the individual phases from an assumedphase composition of the measuring sample. The correspondence betweenthe simulated and measured diffraction pattern can then be effectedthrough determination of covariance.

Rietveld analysis may be conducted using GSAS software as described inLarson et al., “General Structural Analysis System (GSAS)”, Los AlamosNational Laboratory Report LAUR 86-784 (2004) and in Toby, “EXPGUI, AGraphical User Interface for GSAS”, J. Appl. Cryst., 34, 210-221 (2001),both of which are incorporated herein by reference. GSAS and EXPGUI areavailable at https://subversion.xor.aps.anl.gov/trac/EXPGUI/wiki.

The modified Rietveld model includes four phases which can be describedas follows.

Phase Model Parameters Refinement β-MMoO₄ Based on β-FeMoO₄ Unit celland Fe Start from literature occupancies structure: Sleight et al.,Inorg. Chem. 7, 1093-8 (1968) Fe₂(MoO₄)₃ Start from literaturestructure: Chen, Mater. Res. Bull., 14, 1583-90 (1979) m-phase Based onCe₂(MoO₄)₃ Refine unit cell and Ce Start from literature occupanciesstructure: Brixner et al., J. Solid State Chem., 5, 247-9 (1972) t-phaseBased on NaBi(MoO₄)₂ Refine unit cell Start from literature structure:Waskowska et al., Solid State Chem., 178, 2218-24 (2005)

Starting atom coordinates are the same as reported in literaturereferences. Starting lattice parameters are given here and differslightly from the literature values. Thermal displacement parametersU_(iso) are given in units of Å².

β-FeMoO₄, structure described in Sleight et al., Inorg. Chem. 7, 1093-8(1968), which is incorporated herein by reference.

space group C2/m, a=10.194 Å, b=9.229 Å, c=7.012 Å, β=107.08°.

U_(iso) 0.01 for Fe, 0.005 for Mo, 0.02 for O.

Starting Fe occupancies both 1.000.

Fe₂(MoO₄)₃, structure described in Chen, Mater. Res. Bull., 14, 1583-90(1979), which is incorporated herein by reference.

space group P2₁/a, a=15.820 Å, b=9.347 Å, c=18.196 Å, β=125.60°.

U_(iso) 0.01 for Fe and Mo, 0.02 for O.

Ce₂(MoO₄)₃, structure described in Brixner et al., J. Solid State Chem.,5, 247-9 (1972), which is incorporated herein by reference.

space group C2/c, a=16.881 Å, b=11.825 Å, c=15.953 Å, β=108.73°.

U_(iso) 0.01 for Ce and Mo, 0.02 for O.

Starting Ce occupancies all 1.000.

NaBi(MoO₄)₂, structure described in Waskowska et al., Solid State Chem.,178, 2218-24 (2005), which is incorporated herein by reference.

space group I4₁/a, a=5.322 Å, c=11.851 Å.

U_(iso) 0.01 for Mo, 0.02 for Na, Bi, and O.

Background is modeled using either a 3-term cosine Fourier series or a3-term shifted Chebyshev polynomial.

The amorphous component of the catalyst is modeled using seven Debyescattering terms with correction for thermal motion (diffuse scatteringfunction 1 in GSAS). Each term is modeled as an Si—O vector with athermal displacement parameter (U) of 0.05 Å². The Si—O distances of theseven terms are fixed at 1.55, 2.01, 2.53, 2.75, 3.49, 4.23, and 4.97 Å,and their amplitudes are optimized in the Rietveld fit.

The phases and parameters are introduced into the model gradually toensure a stable refinement. At each step, 5-10 cycles of least-squaresrefinement are conducted to allow the model to settle down before thenext components are introduced. A damping factor of 5 (i.e. 50%) on allparameters except the scale factors of the phases is used to reduceovershoots and oscillations. The procedure is as follows:

1. The starting model contains just the β-FeMoO₄ phase with its latticeparameters fixed and its profile Y (Lorentzian lattice strain) set to75. Only the 3-term background function and the scale factor of theβ-FeMoO₄ phase are varied.

2. The shift parameter (sample displacement) is added.

3. The lattice parameters of β-FeMoO₄ are allowed to vary.

4. The other three phases are added, all with fixed lattice parametersand profile X (Lorentzian Scherrer broadening) set to 20, and theirscale factors are allowed to vary.

5. The 7 diffuse scattering terms are added and their amplitudes areallowed to vary.

6. Lattice parameters of the two scheelite-like phases are allowed tovary.

7. Profile Y of β-FeMoO₄ and profile X of the other three phases areallowed to vary.

8. Fe occupancies of the β-FeMoO₄ phase and Ce occupancies of theCe₂(MoO₄)₃ phase are allowed to vary.

9. Least-squares refinement is continued until convergence, i.e. the sumof (shift/esd)² over all parameters is less than 0.01.

Ammoxidation Process

Conversions of propylene to acrylonitrile, hydrogen cyanide andacetonitrile are described in U.S. Ser. No. 13/065,134, filed Mar. 15,2011 and U.S. Ser. Nos. 12/661,705, 12/661,720 and 12/661,716, all filedMar. 23, 2010, which are incorporated herein by reference and summarizedherein.

Catalysts provided herein are useful for conversion of propylene toacrylonitrile, hydrogen cyanide and acetonitrile by reacting in a vaporphase at an elevated temperature and pressure, the propylene with amolecular oxygen containing gas and ammonia in the presence of thecatalyst.

Ammoxidation may be performed in a fluid bed reactor although othertypes of reactors may be utilized. An example of a fluid bed reactorthat may be used is described in U.S. Pat. No. 3,230,246, which isincorporated herein by reference in its entirety. Conditions forammoxidation are know in the art and described, for example, in U.S.Pat. Nos. 5,093,299, 4,863,891, 4,767,878 and 4,503,001, which are eachincorporated herein by reference in their entirety.

Molar ratio of oxygen to olefin in the feed should range from 0.5:1 to4:1, and in another aspect 1:1 to 3:1. The molar ratio of ammonia topropylene in the feed in the reaction may vary between 0.5:1 to 2:1.Suitable feed ratios include an ammonia to propylene molar ratio in therange of 1.0:1 to 1.3:1 and an air to propylene molar ratio of 8.0:1 to12.0:1. The reaction may be carried out at a temperature of about 260°to about 600° C., in another aspect 310° to 500° C., and in anotheraspect about 350° to about 480° C. The contact time is generally notcritical and may be about 0.1 to about 50 seconds, and in another aspectabout 1 to about 15 seconds.

EXAMPLES Example 1 CatalystPreparation—Ni₄Mg₃Fe_(0.9)Rb_(0.192)Cr_(0.05)Bi_(0.72)Ce_(1.76)Mo_(12.502)O_(50.627)+50wt % SiO₂

Reaction mixture A was prepared by heating 1222 ml of deionized water to65° C. and then adding with stirring over 30 minutes ammoniumheptamolybdate (1110 g) to form a clear colorless solution. Silica sol(90 ppm Na, 39 nm avg. particle size, 5461 g, 41.2 wt % silica) was thenadded with stirring.

Reaction mixture B was prepared by heating 241.9 ml of deionized waterto 55° C. and then adding with stirring Fe(NO₃)₃.9H₂O (293.9 g),Ni(NO₃)₂.6H₂0 (940.2 g), Mg(NO₃)₂.6H₂O (621.8 g) and Cr(NO₃)₃.9H₂O (16.2g).

Reaction mixture C was prepared by heating 740.6 ml of deionized waterto 65° C. and then adding with stirring over 30 minutes ammoniumheptamolybdate (673 g) to form a clear colorless solution.

Reaction mixture D was prepared by (i) heating 1560 g of 50 wt % aqueous(NH₄)₂Ce(NO₃)₆ solution to 55° C., and (ii). while the solution wasstirring and heating, sequentially adding Bi(NO₃)₃.5H₂O (282.3 g) andRbNO₃ (22.9 g) resulting in a clear orange solution.

Reaction mixture E was prepared by adding with stirring reaction mixtureB to reaction mixture A.

Reaction mixture F was prepared by adding reaction mixture C to reactionmixture D. This resulted in precipitation of an orange solid. Theresulting mixture was the precipitate slurry. Stirring of Reactionmixture F was continued for 15 minutes while the temperature wasmaintained in the 50-55° C. range.

Reaction mixture F was then added to reaction mixture E to form thefinal catalyst precursor slurry.

The catalyst precursor slurry was allowed to stir for one hour while itcooled to approximately 40° C. It was then homogenized in a blender for3 minutes at 5000 rpm. The slurry was then spray dried at aninlet/outlet temperature of 325/140° C. The resulting powder was heattreated in a rotary calciner under a ramp of 10° C./min to 450° C.,holding one hour, ramping to 560° C. at 10° C./min, holding one hour andfinally cooling to room temperature. The resulting calcined powder wasthen tested as a propylene ammoxidation catalyst.

Example 2 CatalystPreparation—Ni₄Mg₃Fe_(0.9)Rb_(0.192)Cr_(0.05)Bi_(0.72)Ce_(1.76)Mo_(12.502)O_(50.627)+50wt % SiO₂

Reaction mixture A was prepared by heating 9465 ml of deionized water to65° C. and then adding with stirring over 30 minutes ammoniumheptamolybdate (8604 g) to form a clear colorless solution. Silica sol(118 ppm Na, 38.1 nm avg. particle size, 41086 g, 41.4 wt % silica) wasthen added with stirring.

Reaction mixture B was prepared by heating 1828.9 ml of deionized waterto 55° C. and then adding with stirring Fe(NO₃)₃.9H₂O (2221.9 g),Ni(NO₃)₂.6H₂O (7107.9 g), Mg(NO₃)₂.6H₂O (4700.5 g) and Cr(NO₃)₃.9H₂O(122.3 g).

Reaction mixture C was prepared by heating 2686.3 ml of deionized waterto 65° C. and then adding with stirring over 30 minutes ammoniumheptamolybdate (2442 g) to form a clear colorless solution.

Reaction mixture C′ was prepared by heating 2686.3 ml of deionized waterto 65° C. and then adding with stirring over 30 minutes ammoniumheptamolybdate (2442 g) to form a clear colorless solution.

Reaction mixture D was prepared by (i) heating 5896 g of 50 wt % aqueous(NH₄)₂Ce(NO₃)₆ solution to 55° C., and (ii). while the solution wasstirring and heating, sequentially adding Bi(NO₃)₃.5H₂O (1067.1 g) andRbNO₃ (86.5 g) resulting in a clear orange solution.

Reaction mixture D′ was prepared by (i) heating 5896 g of 50 wt %aqueous (NH₄)₂Ce(NO₃)₆ solution to 55° C., and (ii). while the solutionwas stirring and heating, sequentially adding Bi(NO₃)₃.5H₂O (1067.1 g)and RbNO₃ (86.5 g) resulting in a clear orange solution.

Reaction mixture E was prepared by adding with stirring reaction mixtureB to reaction mixture A.

Reaction mixture F was prepared by adding reaction mixture C to reactionmixture D. Reaction mixture F′ was prepared by adding reaction mixtureC′ to reaction mixture D′. In each case this resulted in precipitationof an orange solid. The resulting mixture was the precipitate slurry.Stirring of Reaction mixtures F and F′ was continued for 15 minuteswhile the temperature was maintained in the 50-55° C. range.

Reaction mixture F, followed by reaction mixture F′ were then added toreaction mixture E to form the final catalyst precursor slurry.

The catalyst precursor slurry was allowed to stir for one hour while itcooled to approximately 40° C. It was then homogenized in a blender for3 minutes at 5000 rpm. The slurry was then spray dried at aninlet/outlet temperature of 325/140° C. The resulting powder wasdenitrified in a rotary calciner at 850° F. for 50 min followed bycalcining in a rotary calciner to 1050° F. for 110 minutes. Theresulting calcined powder was then tested as a propylene ammoxidationcatalyst.

Comparative Example 1 CatalystPreparation—Rb_(0.05)K_(0.09)Ni_(5.0)Mg_(2.0)Fe_(1.8)Bi_(0.45)Ce_(0.9)Mo_(12.0)O_(47.4)+50 wt % SiO₂

A 17.9 wt % HNO₃ solution was made by diluting 64 ml concentrated HNO₃to 250.0 ml with deionized water. A 30 wt % silica sol mixture wasprepared by adding 208.3 g deionized water to 625 g 40 wt % SiO₂ sol (22nm avg particle size).

A solution of metal nitrates was prepared by dissolving 70.38Fe(NO₃)₃.9H₂O, 140.73 g Ni(NO₃)₂.6H₂O, 49.63 g Mg(NO₃)₂.6H₂O, 37.82 gCe(NO₃)₃.6H₂O, 21.13 g Bi(NO₃)₃.5H₂O, 0.881 g KNO₃, and 0.714 g RbNO₃ in188.85 g of a 17.9 wt % aqueous nitric acid solution, and heated to 55°C. This metal nitrate solution was added to 833.3 g of the 30 wt % SiO₂sol. To this resulting mixture, a 65° C. solution of 205.04 g of[(NH₄)₂Mo₇O₂₄.4H₂O] in 425 g deionized water was added to form a lightgreen slurry. The slurry was stirred for one hour while cooling to 40°C. The slurry was then transferred to a polyethylene container, agitatedfor 16 hours at room temperature, and spray dried at an inlet/outlettemperature of 325/140° C.

The spray dried catalyst precursor obtained was calcined for one hour ina 400° C. oven and then for two hours in a 590° C. oven. The resultingcalcined powder was then tested as a propylene ammoxidation catalyst.

Results of catalyst testing form all of the Examples was as follows:

wt % wt % m- (m- phase/(m- phase + % % ACN + Example phase + t- ACNHCN + No. t-phase) phase) yield ACN yields Example 1 53.7 24.2 84.0 89.8Example 2 49.4 24.6 82.8 88.9 Comparative 55.5 4.4 78.3 86.0 Example 1

FIG. 1 demonstrates further a trend of increased acrylonitrile yieldwith increasing concentrations of m-phase (expressed as % monoclinicscheelite phase, expressed as weight fraction) in the catalyst. Thescatter in the data is to be expected due to normal experimental errorand differences in the catalyst preparation protocol including batchsize, drying and calcination protocols, some variation in catalystformulation, and experimental error in the quantitative determination ofthe phase composition of the catalyst. The fitted trend line againindicates an increase in acrylonitrile yield as the m-phase (expressedas % monoclinic scheelite) content of the catalyst increases.

Example 3 X-Ray Diffraction Analysis

Catalyst samples were analyzed as received with no grinding. Two piecesof double-sided tape were placed side-by-side on a quartz surface of azero-background cell and the catalyst was sprinkled on the tape to coverit completely. The cell was tapped gently to remove excess catalyst. Theedges of the cell may be cleaned using a paint brush. Typical conditionsfor a Bruker D8 Advance diffractometer were as follows:

-   -   sample spinning    -   Cu Kα radiation    -   X-ray generator 40 KV, 40 mA    -   divergence slit 0.3°    -   antiscattering slit 0.5°    -   Vantec detector discriminator lower level 0.1V, window width        0.5V    -   scan range 5°-100° 2⊖    -   step size 0.00729689°    -   time/step 1 sec    -   total scan time 3:46

While the invention herein disclosed has been described by means ofspecific embodiments, examples and applications thereof, numerousmodifications and variations could be made thereto by those skilled inthe art without departing from the scope of the invention set forth inthe claims.

What is claimed is:
 1. A catalytic composition comprising a complex ofmetal oxides having a formula:Mo₁₂Bi_(a)Fe_(b)A_(c)D_(d)E_(e)F_(f)G_(g)Ce_(h)O_(x) wherein A is atleast one element selected from the group consisting of sodium,potassium, rubidium and cesium; D is at least one element selected fromthe group consisting of nickel, cobalt, manganese, zinc, magnesium,calcium, strontium, cadmium and barium; E is at least one elementselected from the group consisting of chromium, tungsten, boron,aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium andtellurium; F is at least one element selected from the group consistingof a rare earth element, titanium, zirconium, hafnium, niobium,tantalum, aluminum, gallium, indium, thallium, silicon, germanium, andlead; G is at least one element selected from the group consisting ofsilver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinumand mercury; a is from 0.05 to 7; b is from 0.1 to 7; c is from 0.01 to5; d is from 0.1 to 12; e is from 0.01 to 0.1; f is from 0 to 5; g isfrom 0 to 0.2; h is from 0.01 to 5; and x is a number of oxygen atomsrequired to satisfy valence requirements of other component elements,wherein the catalytic composition includes at least about 15% m-phaseplus t-phase by weight and has a weight ratio of m-phase to m-phase plust-phase of 0.45 or greater, where amounts of m-phase and t-phase aredetermined using x-ray diffraction and a modified Rietveld analysismodel, wherein the catalytic composition is effective for providing anacrylonitrile yield (% AN) of 82 or greater and an acrylonitrile yield(% AN) plus acetonitrile yield (% ACN) plus hydrogen cyanide yield (%HCN) of 88 or more.
 2. The catalytic composition of claim 1 wherein themodified Rietveld analysis model includes four major phases.
 3. Thecatalytic composition of claim 1 wherein the catalyst compositionincludes a support selected from the group consisting of silica,alumina, zirconia, titania, or mixtures thereof.
 4. The catalyticcomposition of claim 1 wherein the catalytic composition includes atleast about 18% m-phase plus t-phase by weight.
 5. The catalyticcomposition of claim 4 wherein the catalytic composition includes atleast about 20% m-phase plus t-phase by weight.
 6. The catalyticcomposition of claim 5 wherein the catalytic composition includes atleast about 22% m-phase plus t-phase by weight.
 7. The catalyticcomposition of claim 1 wherein the acrylonitrile yield (% AN) is 83 orgreater.